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PostPosted: Thu Jun 18, 2015 7:46 am 
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Joined: Wed Feb 11, 2015 3:16 pm
Posts: 304
Location: Ontario,Canada
Not sure which one to get for my stock barrelled and powered 2240...the hollow or solid extended probe(.22)? Which one...or better yet,when would I want to choose one over the other.?? Thanks,Huck

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PostPosted: Thu Jun 18, 2015 9:00 am 
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Huck you can make your own extended bolt prob.... :wink:
http://www.network54.com/Forum/275684/t ... e+question

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PostPosted: Thu Jun 18, 2015 10:33 am 
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Location: Ontario,Canada
Ace wrote:
Huck you can make your own extended bolt prob.... :wink:
http://www.network54.com/Forum/275684/t ... e+question

Thanks Ace! I saw that,but I would prefer to buy one already made,but still not sure when I should use a hollow extended probe as opposed to a solid extended probe?. Thanks,Huck

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PostPosted: Thu Jun 18, 2015 4:04 pm 
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Joined: Thu Oct 13, 2005 4:20 pm
Posts: 1549
Location: sherwood park
Hollow Will seat the pellet skirt to the same position every time no matter what pellet you use. And nothing obstructs the path of air or co2 flow so more power potential. I say if crosman and Benjamin were using them in the 50's it must be a good thing. I use hollow in all my custom builds. Harder to make but worth the extra work.


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PostPosted: Thu Jun 18, 2015 4:10 pm 
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Joined: Thu Feb 02, 2006 11:35 pm
Posts: 3099
Location: Alberta Canada
Becomes a choice thing.
The hollow probe will in turn set ALL brands of pellets at the same depth into the rifling. Where as an exrended probe will set different brands at different depths. Its the design inside the skirt that dictates this versus the hollow probe, which uses the skirt base of all brands of pellets.
If your going to play with a multitude of pellets the hollow probe be the choice. If want power and know what is accurate from your gun the extended is the choice.
But then this is just my opinion, I have always favoured the extended.

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PostPosted: Thu Jun 18, 2015 6:44 pm 
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Joined: Tue Oct 13, 2009 1:27 am
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Location: Vancouver
I don't see why power would be sacrificed with a hollow probe. So long as the port on the bottom matches the transfer port size, aligns perfectly with the TP, and the hollowing of the probe is big enough, there's no restriction of flow there. You don't want the hollow going any further back than the back of the TP hole of course as that's wasted area for decompression of the air flow. Shaping that hole with a round bit helps a bit too, bending the air flow around the corner towards the pellet rather than just using a drill bit and going straight in and being done with it. A well made and matched hollow probe with a correctly placed and fitted O-ring should eliminate any restriction of flow while pushing every pellet completely past the TP hole and sealing perfectly so there's no wasted air at the breech. An extended probe can do most of that, with some pellets, so it's the more limited solution.


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PostPosted: Thu Jun 18, 2015 7:45 pm 
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Location: Coalmont BC
Pretty simple, the hollow probe has to clear the chamber and have a thick enough wall to not be too fragile and seat the pellet without cutting the skirt.... Realistically, that means about a 5/32" hole in a .22 cal hollow probe, maybe a few thou larger.... Let's say the hole is 0.160", that leaves an air passage of 0.0201 sq.in.... When I make an extended probe, I use 3/32" in .22 cal.... That has an area of 0.0069 sq.in., subtracted from the bore of 0.22", which is 0.0380 sq.in., leaving 0.0311 sq.in. of area for airflow, over 50% more than with a hollow probe....

I've used both, and have always found that for maximum performance, the extended probe is superior.... However, if the porting in the gun is smaller than the hole you can get in a hollow probe, you may not find any difference in the power.... I have never found any difference in accuracy either.... The best setup for a maximum performance gun with bore-size ports, of course, is a retractable bolt with a flat nose.... The bolt pushes the pellet past the transfer port just like a hollow probe, and then you pull the bolt handle back into a "J" shaped slot, completely clear of the barrel port.... It does require the O-ring inside the barrel, however, instead of riding on the nose of the bolt....

Bob

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PostPosted: Thu Jun 18, 2015 8:23 pm 
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Joined: Tue Oct 13, 2009 1:27 am
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Location: Vancouver
Fair enough for higher powered airguns. But Huck's talking about a "stock barrelled and powered 2240" so the relative efficiency doesn't really come into play. I went to a hollow probe made from steel rod primarily to deal with pellet insertion depth, as my stock 2240 bolt was only pushing JSB Exact 14.3gr pellets about half way over the transfer port hole, leaving half the air coming up and hitting the pellet skirt. Didn't make sense to leave it that way. I also wanted a better seal anyway as there was leakage from the bolt, blowing tissue paper up from the breech quite strongly on firing. No reason an extended probe couldn't do just the same, but when playing around with different pellets as Whitewolf said it makes more sense to use a hollow probe to make sure every pellet design is pushed to the right depth.


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